The present invention relates to waveform display instruments, and more particularly to an equalized eye pattern instrument for extending the usefulness of eye pattern analysis to any point along a digital transmission path.
Although digital systems generally process data in parallel digital form, for transmission over long distances the parallel digital data often is transformed into serial digital data. At the receiving end of such a transmission path the serial digital data is transformed back to parallel digital form. The receiving end of a digital transmission path includes a receiver with an equalizer to return the received data to the form at the transmission end, i.e., the equalizer terminates the transmission path at the receiving end. A waveform display instrument that looks at the data at the receiving end after the equalizer may produce the well known eye pattern that is used to analyze error performance and to optimize the digital signal. However when there is an error along the transmission path that results in no signal at the receiver, it is desirable to be able to display an eye pattern for the signal at any point along the transmission path. For coaxial cable as a transmission medium with a 800 millivolt peak-to-peak input signal after approximately 100 meters it is not possible to obtain an eye pattern of the signal using a conventional waveform display instrument as the signal is attenuated such that it is lost in the noise.
What is desired is a waveform display instrument that may be used to display eye patterns for a digital signal at any point along the transmission path of the digital signal.